docs: def _get_link(element: Element) -> Optional[str]:
      """Attempt to retrieve item link.
  
      Use the GUID as a fallback if it is a permalink.
      """
      link = get_text(element, 'link')
      if link is not None:
          return link
  
      guid = get_child(element, 'guid')
      if guid is not None and guid.attrib.get('isPermaLink') == 'true':
          return get_text(element, 'guid')
  
      return None